The present invention relates to a device for positioning a prosthesis in a bone and a method of implanting a prosthesis.
Various prostheses are known for replacing all or part of a damaged or diseased joint. For example, prostheses for replacing all or a portion of a damaged or diseased knee, hip and shoulder of a person are well known. Often, the joint is replaced by securing one portion of the prosthesis to one bone of the joint and another portion of the prosthesis to another bone.
When reconstructing damaged or diseased joints with artificial prostheses, it is desirable to position the components of the prosthesis such that the structure and function of a properly functioning natural joint is replicated to the greatest degree possible. This involves consideration of several factors. For example, the components of the prosthesis must be inserted such that the patient has the desired limb length after the surgery. It is also desirable that the range of motion of the joint postoperative is, to the extent possible, the same as that of a healthy joint. Some of the factors relevant to proper placement include insertion depth of the prosthesis components into the bone and rotational orientation of the prosthesis components.
The present invention provides an apparatus for positioning a prosthesis in a bone. According to one embodiment of the invention, an apparatus for positioning a prosthesis having a stem in the intramedullary canal of a bone includes a body, a first clamp connected to the body for engaging the bone, a depth gage connected to the body for determining the depth of the prosthesis stem within the intramedullary canal, and a second clamp connected to the depth gage for engaging the prosthesis. The body may include a projection for stabilizing the apparatus when the first clamp engages the bone. A plurality of markings may be provided on the depth gage. The apparatus may include a guide for determining proper rotational orientation of the apparatus relative to the bone. The guide may be selectively secured to and removed from the body. The second clamp may be movable relative to the first clamp. The depth gage may be movable with respect to the first clamp and/or the body. The second clamp may be movable relative to the depth gage. The body may be provided with a channel and the depth gage may be connected to a base that is movable within the channel. The base may include a slot and the channel may include a stop for limiting movement of the base in the channel. The second clamp may be removable from the depth gage and may be engaged with the depth gage in at least two orientations. A cam may be provided for adjusting the first clamp. In one embodiment, the first clamp includes a pair of jaws that engage the shaft of the bone after the soft tissue is removed.
In another embodiment of the present invention, an apparatus for positioning a prosthesis having a stem in the intramedullary canal of a bone having a shaft includes a body, a first clamp for engaging the bone, the first clamp being coupled to the body, a depth gage for determining the depth of insertion of the prosthesis stem in the intramedullary canal, the depth gage being coupled to the body and moveable relative to the body in a direction generally perpendicular to the shaft of the bone, and a second clamp for engaging the prosthesis, the second clamp being coupled to the depth gage for movement therewith and being movable relative to the body in a first direction generally parallel to the shaft of the bone.
According to another embodiment of the present invention, an apparatus for positioning a prosthesis having a stem in the intermedullary canal of a bone includes first means for selectively attaching the apparatus to the bone, second means for determining the depth of insertion of the prosthesis stem in the intramedullary canal, the second means being coupled to the first means, third means for selectively engaging the prosthesis, the third means being coupled to the second means, fourth means for permitting movement of the third means relative to the first means in a first direction, and fifth means for permitting movement of the third means relative to the first means in a second direction. The first means may include a clamp and a cam for operating the clamp. The second means may include a post, which may include at least one marking. The third means may include a clamp. The fourth means may include a post and an opening in the third means that engages the post. The fifth means may include a body moveable within a channel and the third means may be coupled to the body. The apparatus may also include a stop in the channel for limiting movement of the body.
According to another embodiment of the invention, a method of implanting a prosthesis having a stem in the intramedullary canal of a bone includes the steps of reaming the intramedullary canal to accommodate at least a portion of the stem, providing an apparatus having a first clamp, a second clamp, a depth gage and a guide, using the guide to establish the proper rotational orientation of the apparatus, securing the first clamp to the bone, securing the second clamp to the prosthesis, coupling the second clamp to the depth gage, inserting the stem into the intramedullary canal, and reducing the joint.
Other features of the present invention will be apparent to those skilled in the art from the detailed description of the preferred embodiments and the accompanying drawings.